An etching process for high-aspect ratio (HAR) structure is one of key technologies in the recent semiconductor device fabrication. In the development and control of etching processes, it is very critical to evaluate depth, shape profile, and tilting. Critical dimension small angle X-ray scattering (CD-SAXS) is a powerful measurement technique to characterize such shape parameters of HAR structures. In this paper, we evaluated the measurement sensitivity of CD-SAXS for changing shape parameters (average CD, depth, side wall shape, tilting) of HAR holes using simulation results. The simulation results show that CD-SAXS has sufficient sensitivity to characterize shape parameters of HAR structures. We also demonstrated the performance of CD-SAXS by measurement of 1μm depth holes on the 300 mm wafer. As a result, we were able to obtain detailed hole profiles, distribution of average CD and tilt angle across the entire wafer.
KEYWORDS: Tin, X-rays, Scattering, Transmission electron microscopy, Semiconducting wafers, 3D modeling, X-ray detectors, 3D metrology, Silicon, Film thickness
We have evaluated two types of high aspect ratio (HAR) structures of semiconductor memory devices by adopting small-angle x-ray scattering in transmission geometry (T-SAXS). One is the thin TiN thickness on the sidewall of 1.4 μm deep holes. The results indicate that T-SAXS is capable of determining sidewall thickness profiles with sub-nanometer accuracy. The other is the precise three-dimensional shape of 4.2 μm deep holes. The results show that the shape of the hole cross-section parallel to the sample surface changes drastically in the depth direction. These evaluation results of the two structures are consistent with that of transmission electron microscope, respectively.
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